An intraocular lens is commonly used to replace the natural lens of the human eye when warranted by medical conditions. It is common practice to implant an IOL in a region of the eye known as the capsular bag or posterior capsule.
One problem that is experienced with many IOL""s following their implantation is that cells from the eye, particularly lens epithelial cells from the capsular bag, tend to grow on the capsular bag in front of and/or in back of the optical portion of the IOL. This tends to block the optical portion of the IOL and to impair vision.
A common treatment for this condition is to use a laser to destroy the cells and a central region of the capsular bag. Although this treatment is effective, the laser is expensive and is not available throughout the world. There is also cost associated with the laser treatment as well as some patient inconvenience and risk of complications. Finally, the laser treatment may affect the performance of some IOL""s.
Davenport U.S. Pat. No. 4,743,254 discloses an IOL which includes glare reducing sections on the opposite sides of an optic. These glare reducing sections are fully or partially opaque and their surfaces are not smooth. It has been observed that cell migration across the glare reducing sections appears to be reduced. A similar result has been observed in a plate IOL in which a plate, which is used as a haptic for fixing the IOL in the eye, surrounds the optic. Specifically cell migration across the plate, which has a somewhat textured surface, appears to be reduced.
Kelman U.S. Pat. No. 4,808,181 discloses an IOL including a lens assembly having an anterior surface formation and a posterior surface formation. At least a portion of the posterior surface formation constitutes a planar contact region adapted to seat against the posterior capsule of the eye to permanently anchor the lens assembly. The contact region is provided with a roughened surface area defined by a series of ordered narrow linear depressions extending transverse of the plane of the contact region. This patent teaches that these ordered narrow linear depressions accelerate adhesion and enhance anchoring of the tissue of the posterior capsule to the lens assembly. This patent is not concerned with secondary opacification and provides no solution to this problem.
This invention provides an IOL which is believed to solve the secondary opacification problem discussed above. With this invention, an optical portion, which is adapted to be placed in the capsular bag of an eye, directs light toward the retina of the eye, and a cell barrier portion circumscribes the optical portion. With this construction, the optical portion serves the normal function of directing and focusing light at or near the retina. The cell barrier portion inhibits cell growth from the eye, for example, from the capsular bag, in front of and/or in back of (behind) the optical portion. The optical portion and the cell barrier portion may be considered as being portions of the optic.
The cell barrier portion of the optic circumscribes the optical portion so as to not leave any path available for the migration of cells in front of or in back of the optical portion. The cell barrier portion is constructed so as to be incapable of or ineffective in focusing light on the retina. The cell barrier portion is preferably partially or wholly opaque to eliminate light scattering.
At least one fixation member, preferably an elongated fixation member, is coupled to, and preferably extends outwardly from, the optic for use in fixing the optic in the eye. Viewed from a different perspective, a structure other than the cell barrier portion is employed for fixing the optic in the eye. Such structure may include one or more fixation members of various different configurations coupled to the optic. The fixation members may be separate members attached to the optic or members which are integral with the optic, and they may comprise elongated filaments or one or more wider plate or plate-like members.
The cell barrier portion may be of any construction which performs the function of inhibiting cell growth from the eye in front of or in back of the optical portion. In this regard, the cell barrier portion may include an irregularly configured structure or surface feature, such as an irregularly roughened or textured surface region and/or one or more annular grooves which are at least partially defined by irregular surfaces.
As-used herein, the terms xe2x80x9cirregularxe2x80x9d or xe2x80x9cirregularlyxe2x80x9d refer to a thing, for example, an irregularly roughened surface region, or series of things, for example, irregular surfaces, which do not have a consistent order, pattern or configuration. In one embodiment, these terms refer to a thing or series of things which are substantially unordered or which have a pattern or configuration with a significant or substantial degree of randomness, or even substantially complete randomness. With particular regard to the annular groove or grooves described herein, the irregular surfaces which at least partially define, preferably which define a major portion of and more preferably which substantially completely define, such groove or grooves are represented by other than straight lines, for example, other than straight lines having a length more than about 0.001 mm or about 0.0005 mm, with the groove or grooves viewed in axial cross-section, that is in cross-section along a plane which includes the central optical axis of the optical portion. The annular grooves are not to be considered regular simply because they are present in a concentric array with each groove being substantially equally spaced apart from the adjacent groove or grooves. In one embodiment, the irregularity in accordance with the present invention is sufficient to result in the irregularly configured structure, present in an otherwise optically clear cell barrier portion to be at least about 50% opaque (that is frosty or hazy), more preferably at least about 80% opaque and still more preferably substantially completely opaque.
The irregularly configured structure or surface feature of the cell barrier portion preferably has a radial dimension of no more than about 2 mm, more preferably no more than about 0.75 mm and still more preferably no more than about 0.25 mm. If the cell barrier portion includes an annular groove, the groove preferably has a maximum width and a maximum depth each no greater than about 0.02 mm. In one preferred construction, the cell barrier portion includes at least about 20 annular grooves.
The optic has anterior and posterior faces. The irregularly configured structure, for example, surface roughening or texturing and/or grooves, may be provided on any surface or surfaces along which the cells may migrate and completely circumscribes the optical portion. Preferably, the irregularly configured structure is provided at least on the posterior face and/or anterior face of the optic in the cell barrier portion.
The irregularly configured structure or surface feature can be included in/on the cell barrier portion using any suitable technique or methodology. Of course, it is important that this structure or surface feature be sufficiently irregular to achieve the desired inhibition of cell migration or cell growth so that the risk of secondary opacification is reduced. The technique or methodology chosen to include this structure or surface feature should take this basic criterion into account. This structure or surface feature can be formed during the initial formation, for example, the molding, of the cell barrier portion or optic, or can be included after the cell barrier portion or optic is produced, for example, using a laser, lathe, other mechanical implement and the like. In one particularly useful embodiment, a lathe is employed to form a spiral array of annular grooves defined by irregular surfaces in the cell barrier portion. Cell barrier portions may be processed in a manner similar to the glare reducing sections of Davenport U.S. Pat. No. 4,743,254 to yield fully or partially opaque structures the surfaces of which are irregular and not smooth. The disclosure of this patent is incorporated in its entirety herein by reference.
The cell barrier portion may be integral with the optical portion, or may be a separate member coupled to the optical portion. Also, the fixation member or members may be integral with the cell barrier portion and/or the optical portion, or may be a separate element or elements, e.g., filament or filaments, coupled to the optical portion or the cell barrier portion.
The invention, together with additional features and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying illustrative drawings.